It is desirable to provide high wear and buckling resistance in power transmission belts by improving the formulation of the composition of rubber portions of the belt. Such belts may conventionally comprise frictional transmission belts, such as V-shaped or V-ribbed belts, or toothed belts.
It is further desirable to minimize maintenance and cost in the use of such drive belts by providing belts which have long, troublefree life while transmitting high loads.
It has been found that the achievement of these desirable characteristics may be effected by providing in the belt high elasticity and wear resistance in the transverse direction and high bending resistance in the longitudinal direction.
It has been conventional to mix carbon black with the rubber in such belts to improve the wear resistance thereof. Further, it has been conventional to provide cut fibers of cotton, nylon, polyester, etc., in the rubber composition oriented transversely of the belt and utilized as the compression layer portion of the belt.
Another method of improving the power transmission characteristics of such belt is to utilize in the compression layer portion rubber mixed with graphite.
Such additives have also been employed in the tension portion of the belt to improve the wear resistance.
A problem arises in the use of high quantities of carbon black in that substantial heat is generated during the operation of such belts and the useful lifetime of the belt may be decreased due to the decreased bendability.
Similarly, where a large quantity of cut fibers is provided extending transversely across the belt, internal heat is generated and the bendability decreases, thereby shortening the useful life of the belt. Similar problems arise in the use of graphite in this manner.